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std/collections/running_reduce.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** * Calls the given reducer on each element of the given collection, passing its * result as the accumulator to the next respective call, starting with the * given initialValue. Returns all intermediate accumulator results. * * @example * ```ts * import { runningReduce } from "https://deno.land/std@$STD_VERSION/collections/running_reduce.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/assert/assert_equals.ts"; * * const numbers = [1, 2, 3, 4, 5]; * const sumSteps = runningReduce(numbers, (sum, current) => sum + current, 0); * * assertEquals(sumSteps, [1, 3, 6, 10, 15]); * ``` */export function runningReduce<T, O>( array: readonly T[], reducer: (accumulator: O, current: T, currentIndex: number) => O, initialValue: O,): O[] { let currentResult = initialValue; return array.map((el, currentIndex) => currentResult = reducer(currentResult, el, currentIndex) );}